Golf club device

ABSTRACT

A golf club device, more specifically a putter ( 1 ), comprising a head ( 2 ) and a shaft ( 3 ) attached to the head ( 2 ), the free end of the shaft ( 3 ) possibly being provided with a grip, wherein the moment of mass inertia of the head ( 2 ) constitutes less than seventy-nine per cent of the total moment of inertia of the putter ( 1 ) when the putter ( 1 ) is rotated about an axis of rotation ( 4 ), which is perpendicular to the longitudinal axis ( 7 ) of the shaft ( 3 ) and about one hundred and twenty centimeters from the longitudinal axis ( 5 ) of the head ( 2 ), and/or wherein the mass of the shaft, including a possible displaceable weight ( 11 ), divided by the length of the shaft is at least one hundred and seventy grams per meter of shaft in a shaft which is up to one meter long, and at least one hundred and ninety grams per meter of shaft in a shaft which is longer than one meter.

CROSS REFERENCE TO RELATED APPLICATION

The present application is the U.S. national stage application ofInternational Application PCT/NO02003/000277, filed Aug. 15, 2003, whichinternational application was published on Feb. 26, 2004 asInternational Publication WO 2004/016326. The International Applicationclaims priority of Norwegian Patent Application 20023882, filed Aug. 16,2002.

BACKGROUND OF THE INVENTION

The invention relates to a golf club device, more specifically aso-called putter, which is used to hit the golf ball the last distanceto a hole.

A putter is used in order to hit a golf ball a relatively shortdistance, typically from a few millimeters to about thirty meters. Theputter is arranged with a club face, which is nearly perpendicularrelative to the ground surface when the putter hits the ball, in orderfor the ball to roll along the ground.

Golf clubs that are used in competition, must have a configuration inaccordance with the rules that apply to the game of golf. Technicalsolutions are known, which may help the player to achieve optimalstrokes, but the set of rules allows limited freedom of action in termsof technical means.

Known optimization of golf clubs includes variations in the angle of theclub face, the mass and shape of the club head, the mass, shape andrigidity of the shaft, the position of the center of gravity of the clubhead relative to the position of the shaft attachment and the pointwhere the face is to hit the ball, etc.

In putting it is most important that the ball is hit in such a way thatit gets the right initial velocity and direction in order for the balljust to reach the hole. The initial velocity is affected by threeconditions: the velocity of the club head as it hits the ball, theeffective mass of the putter and the position of the hitting point onthe face of the club head.

Given the effective mass of the putter, it is the player's ability tocontrol the velocity of the club head and the hitting point thatdistinguishes a good putt from a not so good putt. The greatesttransmission of energy from club to ball is achieved when the hittingpoint on the face of the club head is on the course of the centre ofgravity of the club head. With minor variations, a good player willplace the hitting point correctly, players practicing to get it to bethe same from one stroke to the other. To a trained player the greatestchallenge is therefore to get the right velocity for the club head, sothat the ball gets the right initial velocity.

When putting is performed by wrist rotation, the player grips the clubwith both hands at the free end of the shaft and holds the club right infront of himself as he is bending forward. By a rotation of the wrists,the club is rotated about an essentially horizontal axis of rotation atthe wrists, and the stroke is performed without the back and theshoulder portion moving. When putting is performed by a rotation of thevertebral column, the club is gripped in a way corresponding to that inwrist rotation, but the stroke movement is achieved by a rotation of theupper body about the vertebral column. The club rotates about anessentially horizontal axis at the height of the top of the vertebralcolumn. Experienced golfers prefer to perform a putt by rotation of thevertebral column. Wrist putting is more common among novices.

A putt normally requires very little energy, a small part of a trainedplayer's stroke capacity is involved. More often than not, putts arecarried out at a very low club velocity. It is difficult to adjust thetransmission of energy in the stroke. To increase the stability of theputter in the stroke, known putters have a light shaft and a relativelyheavy club head, and the development has been towards heavier andheavier club heads. The club head of a putter weighs from 250 to 500grams, whereas the shaft typically weighs from 100 to 120 grams. Anincreased mass of the club head has a stabilizing effect, but it isstill difficult to achieve the right initial velocity on the golf ball.This may be caused by the fact that a heavy club head means an increasedactive mass transmitting energy to the ball, and even small velocitydifferences in the moment of striking make noticeable differences in theinitial velocity of the ball.

SUMMARY OF THE INVENTION

The object of the invention is to provide an improved putter.

The object is realized through features as specified in the descriptionbelow and the following claims.

A putter according to the invention is stabilized by the shaft having alarge mass compared to that of known putters, either by the shaft makingup a larger part and the club head a smaller part of the moment of massinertia of the putter about a defined axis of rotation, than in a knownputter, or by the mass of the shaft per unit of length being larger thanin a known putter.

A putter according to a first embodiment of the invention is providedwith a club head, which has an average or small mass, so that the head'spart of the moment of mass inertia of the putter about the axis ofrotation makes up a smaller part of the total moment of mass inertia ofthe putter than in known putters.

A putter according to a second embodiment of the invention is providedwith a shaft which has a larger mass per unit of length than knownputters have.

The moment of inertia of a mass point rotating about an axis of rotationis defined as the mass of the mass point multiplied by the square of thedistance between the mass point and the axis of rotation. When a bodyrotates about an axis of rotation, each mass point of the body willfollow its own course, so that the distance of said axis of rotation canvary from one mass point to another. There is a well developed set offormulas for the calculation of the moment of inertia of bodies rotatingabout an axis, and this is well known to a person skilled in the art.Therefore, the theoretical basis for the moment of inertia andcalculations associated with it, will not be explained in furtherdetail.

A putter according to the invention may have a club head of any mass. Atypical putter can have a club head with a mass in the range of 225 to350 grams and a shaft with a mass in the range of 150 to 1500 grams ormore. At the free end of the shaft there is arranged, in a known manner,a grip with a mass in the range of 56 to 141 grams. According to a firstembodiment of the invention the club head makes up less than 80 percentof the moment of inertia of the club when the club rotates about an axisof rotation perpendicular to the shaft and at a distance of about 120centimeters from the club head. The shaft may be provided with adisplaceable mass, for example in the form of a tubular sleeve enclosingthe shaft, the sleeve being arranged to be attached at a desireddistance from the club head. The shaft's portion of the moment ofinertia can thereby be adjusted to the player's stroke technique.

In practice the club head's portion of the moment of inertia of theputter about the axis of rotation may be between 30 and 75 percent. Thisis significantly different from known putters, in which the club headmakes up 80 percent or more of the moment of mass inertia of the clubwhen the club is rotated about a rotational axis as indicated.

The mass of the shaft may be determined through the choice of materialand the dimensioning. Additional masses may also be provided in the formof weights or filling substance in a tubular shaft. The additional massmay be displaceable longitudinally of the shaft, for example adisplaceable weight arranged either on the shaft or within a tubularshaft. The moment of inertia of the shaft about the axis of rotation,may be adjusted to a preferred value through displacement of the weight.

According to the invention, the connection between the head and shaft ofthe putter may advantageously be formed as a connection of limitedelasticity. As the head of the putter hits the ball, said elasticconnection contributes to that mainly the mass of the head gives theball its initial velocity, whereas the mass of the shaft will be lessimportant.

As mentioned, the purpose of the invention can be realized through aputter according to a second embodiment of the invention, morespecifically by means of a shaft of a relatively large mass per unit oflength. The total mass of the shaft comprises the shaft and a possibledisplaceable weight. More specifically, the total mass of the shaftdivided by the length of the shaft should be at least 170 grams permeter of shaft in shafts shorter than 1 meter, and at least 190 gramsper meter of shaft in shafts longer than 1 meter.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in further detail below by means of anexemplary embodiment, and reference is made to the attached drawings, inwhich:

FIG. 1 shows in perspective a generalized putter with a cylindricalshaft;

FIG. 2 shows a front view of the putter of FIG. 1;

FIG. 3 shows a front view of a putter with a displaceable weight on theshaft;

FIG. 4 shows a front view of a putter with a conical shaft;

FIG. 5 shows, in a front view and on a larger scale, a section through aputter head and part of a shaft.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1 the reference numeral 1 identifies a generalized puttercomprising a head and a cylindrical shaft 3 attached to the head 2.FIGS. 1 and 2 will be used to support reflections connected to themoment of mass inertia of the putter 1 and how it is divided between thehead 2 and the shaft 3. To simplify the description, moment of inertiais used instead of moment of mass inertia below. At the free end of theshaft 1 a grip is arranged in a known manner, but this has not beenshown as it affects the reflections to a small degree and is not ofimportance to the conclusions.

In FIGS. 1 and 2 the head 2 and the shaft 3 have been simplified to amassive straight cylindrical shape to simplify the following reflectionon the moment of inertia of the putter 1.

In a stroke, the putter 1 is rotated about an essentially horizontalaxis of rotation 4 located about 120 centimeters from the axis 5 of theclub head 2. The length of the head 2 has been chosen to be 12centimeters and the diameter has been chosen to be 3 centimeters. Agreat number of heads of greatly varying shapes are known. For a givenmass, a cylindrical shape with the specified dimensions represents aputter head with a low moment of inertia about the longitudinal axis.The distance between the axis of rotation 4 and the longitudinal axis 5of the head 2 will vary with the player's height and manner of playing.

The diameter of the shaft 3 has been chosen to be 1 centimeter. Thelength of the shaft 3 has been chosen to be 88 centimeters, whichcorresponds to a good thirty-four inches.

A transversal axis 6 halfway along the length of the shaft 3 is thereby75 centimeters from the axis of rotation 4 and 45 centimeters from theaxis 5 of the club head.

The structure of the generalized putter 1 has otherwise been chosen tobe such that the axis of rotation 4, the longitudinal axis 5 of the headand the transversal axis 6 of the shaft are perpendicular to thelongitudinal axis 7 of the shaft 3.

In a stroke the putter 1 is rotated like a pendulum, approximately assuggested in broken lines in FIG. 2, in which the head 2 describes anarc 8, whereas the free end of the shaft 3 describes an arc 9 and thecenter of the shaft 3 describes an arc 10.

The mass of the shaft 3 has been set at 0.15 kilograms, which isconsidered to be representative of a known putter. The mass of the head2 has a great effect on the moment of inertia of the putter 1.Therefore, it is reasonable to look at the division of the moment ofinertia between the head 2 and the shaft 3 for two values of the mass ofthe head 2, the selected values representing extreme values for atraditional putter, namely 0.25 and 0.5 kilograms respectively.

According to Steiner's theorem, the moment of inertia of the head 2about the axis of rotation 4 is given by the sum of the moment ofinertia of the head 2 about the longitudinal axis 5 of the head and themoment of inertia of the center of gravity of the head 2 about the axisof rotation 4. Correspondingly, the moment of inertia of the shaft 3about the axis of rotation 4 is given by the sum of the moment ofinertia of the shaft 3 about the transversal axis 6 and the moment ofinertia of the center of gravity of the shaft 3 about the axis ofrotation 4. With the indexes h for the head and s for the shaft, themoment of inertia I can be expressed through formulas as given below, inwhich the letters m, d, l and a indicate mass, diameter, length anddistance to the axis of rotation, respectively.

$I_{h} = {{{\frac{m_{h}}{2}\frac{d_{h}^{2}}{4}} + {m_{h}a_{h}^{2}}} = {m_{h}\left( {\frac{d_{h}^{2}}{8} + a_{h}^{2}} \right)}}$$I_{s} = {{{\frac{m_{s}}{12}\left( {{\frac{3}{4}d_{s}^{2}} + l_{s}^{2}} \right)} + {m_{s}a_{s}^{2}}} = {m_{s}\left( {\frac{d_{s}^{2}}{16} + \frac{l_{s}^{2}}{12} + a_{s}^{2}} \right)}}$

By inserting the numerical values d_(h)=3 cm, l_(h)=12 cm, a_(h)=120 cmfor a first head 2 having a mass m_(h)=0.25 kg and for a second head 2having a mass m_(h)=0.5 kg, it can be seen that for a known putter 1 themoment of inertia of the head 2 about the axis of rotation 4 will be inthe range of 3600-7200 kgcm².

For the shaft 3 are used, correspondingly, d_(s)=1 cm, l_(s)=88 cm,a_(s)=75 cm and mass m_(s)=0.15 kg, which gives a moment of inertia ofthe shaft 3 about the axis of rotation 4 equalling 941 kgcm².

Thus, the total moment of inertia I=I_(h)+I_(s) of a known putter 1 willbe in the range of 4541-8141 kgcm² when the head 2 weighs from 0.25 to0.5 kg. Thereby, the head 2 makes up 79-88 percent of the total momentof inertia.

For a putter 1 according to the invention, the head 2 will constitute asmaller portion, and the shaft 3 will constitute a larger portion of thetotal moment of inertia of the putter 1 than for a known putter.

By increasing the mass of the shaft 3 from 0.15 kg to 0.2 kg, forexample, both the moment of inertia of the shaft 3 and the total momentof inertia of the putter about the axis of rotation 4 will increase. Ifthe mass of the head 2 is 0.25 kg, the portion of the head 2 of thetotal moment of inertia is reduced from 79 to 74 percent. If the mass ofthe head 2 is 0.5 kg, the portion of the head 2 of the total moment ofinertia is reduced from 88 to 85 percent.

If the mass of the shaft 3 is increased to 1.5 kg, the portion of thehead 2 of the total moment of inertia about the axis of rotation 4 willbe 28 and 43 percent, respectively, for a head 2 with a mass of 0.25 or0.5 kg.

For a putter 1 according to the invention, the moment of inertia of thehead 2 about the axis of rotation 4 makes up less than 79 percent of thetotal moment of inertia of the putter about the axis of rotation 4 whenthe distance between the axis of rotation 4 and the longitudinal axis 5of the head 2 is about 120 centimeters. The head's 2 portion of themoment of inertia may advantageously be less than 75 percent.

In FIG. 3 is shown a putter 1, in which the shaft 3 is provided with aweight 11 arranged to be displaced along the shaft 3 and attached at adesired distance from the head 2. The weight 11 will form part of thetotal moment of inertia of the putter 1 about the axis of rotation 4 andthereby contribute to reduce the portion of the head 2 of the totalmoment of inertia. The moment of inertia of the weight 11 is determinedby the mass of the weight 11 and its distance to the axis of rotation 4.Thereby, the head's 2 portion of the total moment of inertia can beadjusted through displacement of the weight 11.

FIG. 4 shows an embodiment of a putter 1, in which the shaft 3 isconical, so that the diameter of the shaft 3 is the largest at its freeend and the smallest at the head 2. In practice the shaft 3 will beprovided with a suitable grip at the free end of the shaft 3, but thegrip is not shown. A conical shaft 3 will provide a different massdistribution and moment of inertia from those of a cylindrical shaft ofthe same mass and the same length. The moment of inertia of the conicalshaft 3 about the axis of rotation 4 is lower than that of acorresponding cylindrical shaft. This is essentially due to the factthat the center of gravity of the shaft is moved closer to the free endof the shaft 3 and thereby closer to the axis of rotation 4. To maintainthe head's 2 portion of the total moment of inertia, the moment ofinertia of the head 2 must also be lower when a conical shaft is used,as is shown in FIG. 4. This means that the mass of the head 2 must besmaller when a conical shaft 3 is used. The shaft 3 of the putter 1 willtypically have a circular cross-section, whether the shaft iscylindrical or conical, but a different cross-sectional shape can alsobe used.

FIG. 5 shows a section through a head 2, in which a shaft 3 is insertedinto a bore 12 of the head 2 and secured to the head 2 by an elasticmaterial 13, which is disposed in an annular space between the head 2and the shaft 3. The elastic material 13 may be, for example, a ring ofrubber glued to the shaft 3 and to the head 2. The elastic material 13may also be an elastic moulding substance. With an elastic connectionbetween the head 2 and the shaft 3, the contribution from the mass ofthe shaft 3 in the stroke is reduced.

1. A golf putter comprising: a head; a grip; and a shaft consisting ofan elongated member having a unitary construction, the member having afirst end coupled to the head and a second end coupled to the grip,wherein the weight of the shaft is uniformly distributed along itslength between the first and second ends; wherein the moment of massinertia of the head constitutes less than seventy-nine percent of thecombined mass of inertia of the head and the shaft when the head, shaftand grip are pivoted about a pivot axis that is generally perpendicularto the longitudinal axis of the shaft and that is situated about onehundred and twenty centimeters from the longitudinal axis of the head.2. The golf putter of claim 1, wherein the shaft is a straightcylindrical shape and wherein the mass of the shaft is evenlydistributed along the entire length of the shaft.
 3. The golf putter ofclaim 1, wherein the shaft is a conical shape and wherein the mass ofthe shaft is evenly graduated along the entire length of the shaft. 4.The golf putter of claim 3, wherein the weight of the shaft increasesgradually along the length of the shaft from its second end to its firstend.
 5. The golf putter of claim 1, wherein the moment of mass inertiaof the head constitutes greater than thirty percent of the total momentof inertia of the head, the grip and the shaft.
 6. The golf putter ofclaim 1, wherein the mass of the shaft divided by the length of theshaft is at least one hundred and seventy grams per meter of shaft in ashaft which is up to one meter long and at least one hundred and ninetygrams per meter of shaft in a shaft which is longer than one meter.